Reinitiation of normal reproductive cycles after pregnancy appears to resemble a miniature :puberty." The postpartum women is utilized as a model to test the hypothesis that the GnRH pulse generator is inhibited by the opioidergic system during pregnancy. Using the neuropharacogic probe Naloxone of pulsatile receptor antagonist, we are evaluating for an earlier recovery of pulsatile GnRH-LH secretion in this group of women.